1. Field of the Invention
The invention concerns a flat strip lamella for reinforcing load-bearing or weight-transferring building components, having a composite structure consisting of a plurality of pliant or loose-flex supporting fibers and a binder matrix which connects the supporting fibers to each other and which is fastenable by its broad side by means of an adhesive to the surface of the building component. The invention further concerns a process for production of this type of flat strip lamella.
2. Description of the Related Art
Reinforcing lamellas of this type are known for example from WO 96/21785. The reinforcing lamellas are applied to longitudinally extending and/or areal or laminar building components. The binder matrix which is comprised of a stiff elastic Duroplast, for example of epoxy resin, does not make it possible to introduce bends with small bend radius, so that it is not possible to form bow or bracket type reinforcements over an edge or corner of a building component. Bracket or bow-like reinforcements are required for example in the case of concrete reinforced beams or concrete slab T-beams to secure the relationship between the compressive and tensile zones and to avoid shear and transverse fractures.
Beginning therewith the invention is concerned of a task of developing a flat strip lamella which makes possible a corner overlapping reinforcement of construction components. A further task of the invention is comprised in the development of processes for production of this type of flat strip lamella.
According to a first embodiment of the invention a so-called corner lamella is proposed, which comprises two lamella side pieces which are united with each other into a single piece along an edge running perpendicular to the longitudinal direction of the reinforcing fibers and defining an angle of from 30xc2x0 to 100xc2x0 with respect to each other. Since the building components to be reinforced are primary formed as right angles, the sides of the lamella form an angle of 90xc2x0 to each other. In order dissipate stress forces over the right angles without danger of fracturing, the right angle corner between the lamella side pieces is preferably formed with a radius of curvature of 5 to 50 mm, preferably 15 to 30 mm.
As for the manufacture of this type of angled lamella, there are various possibilities. It has been found to be particularly advantageous when a first longitudinally extending flat strip lamella completely permeated with binder matrix is, at least in an intermediate area, subjected to a bending press at a temperature above the glass transition temperature, preferably at a temperature of 300xc2x0 C. to 600xc2x0 C., under formation of two lamella side pieces joined to each other at a corner forming an angle with each other, and subsequently cooled to a lower use temperature under temporary maintenance of the pressure force.
A further inventive variation of the process for manufacture of the angular lamella is comprised therein, that a fiber cord or web comprised of reinforcing fibers is wrapped in a spiral manner about a support body with preferably quadratic or square circumference and is fixed thereto in the wound state, that the wound fiber cord is impregnated with a fluid plastic resin thereby forming a binder matrix, that the plastic resin is hardened to form a composite material tube preferably shaped as a four cornered tube, and that the composite material tube, in certain cases after removal of the support body, is separated crosswise and longitudinally multiple times with formation of the angular lamella with reinforcing fibers extending in the longitudinal direction.
A third inventive variation of the method of manufacture of the angular lamella is comprised therein, that one cord or one web of reinforcing fibers is introduced crosswise into a casting mould with a cavity having a right angled cross section, so that in the cavity fluid binder resin can be injected or poured in for impregnation of the reinforcing fibers, so that the binder material resin is hardened, preferably under the action of pressure and heat, and that subsequently the thereby formed finished angular lamella is removed from the casting mould.
The inventive angle lamellas can be employed for thrust reinforcement, tensile reinforcement or buckle reinforcement of steel reinforced concrete supporting beams, studs or girders, wherein the two side pieces which are at angles to each other are adhered with an adhesive material to two surfaces of a building component forming a corresponding angle with each other. For lengthening of the reinforcing lamella there can be adhered by overlapping with an adhesive layer, on at least one of the lamella side pieces, a second flat strip lamella to be bonded to the appropriate building component surface. Likewise also multiple flat strip lamellas can be overlapped at their free side piece ends and adhered with each other and with the construction component thereby forming a closed lamella ring circumscribing the construction component.
In order that a preformed, longitudinally extending flat strip lamella can be extended over construction component edges, there is proposed in accordance with an alternative embodiment of the invention, to remove the binder matrix in at least one intermediate area, laying bare the reinforcing fibers. The bare reinforcing fibers can be bowed or bent over a preferably rounded-off fixed body or construction component edge and in this condition be impregnated with a fluid or pasty hardenable resin in the area of the exposed reinforcing fibers. The hardened resin stabilizes the previously exposed reinforcing fibers in the condition of being bent over the edge.
The reinforcing fibers are preferably formed of carbon fibers, which are characterized by a high modulus of elasticity. The reinforcing fibers can however contain or be comprised of aramid fibers, glass fibers, polypropylene fibers and the like.
The binder matrix and the synthetic resin subsequently provided upon the exposed reinforcing fibers is preferably of a Duroplast, preferably of epoxy resin, polyurethane resin or polyester resin.
For the production of flat strip lamellas with flexible intermediate areas first an area of lamella completely impregnated with binder matrix is heated at least in the defined intermediate area to a decomposition temperature of the binder and thereby the binder matrix is removed with exposure of the reinforcing fibers. In the case of employment of epoxy resin as the binder the flat strip lamella is heated in the intermediate area to a temperature of between 300xc2x0 C. and 750xc2x0 C. Thereafter the flat strip lamella is bent in the intermediate area about a corner of a fixed body or a construction component and before or subsequently impregnated with a hardenable synthetic resin, preferably an epoxy resin.
The inventive flat strip lamellas can be employed for compression reinforcement, tensile reinforcement or buckling reinforcement of steel reinforced concrete beams, studs or girders, wherein the flat strip lamellas are bent in their binder-free intermediate areas about the corners of a construction component and in their bent condition are acted upon by a hardenable resin. In the case that the angle of bending of the edges is too small, the construction components can be provided on their corners with a molding or rounding out piece which increases the radius of the curvature of the corner, prior to application of the flat strip lamella.